In the eye, a healthy, intact retina is key to clear vision.
Macular neovascular membranes (MNV) are new, damaging blood vessels that grow inside or beneath the retina, in an area called the choroid. When these vessels leak clear fluid or bleed inside or under the retina they cause vision loss.
MNV are associated with many serious eye diseases, most commonly wet age-related macular degeneration. MNV are also found in those with various conditions such as histoplasmosis, myopic macular degeneration, eye injury and many others.
If you have MNV, you may experience painless vision loss. You may notice blank spots in your vision, especially your central vision. Your vision may be distorted, so that straight lines appear bent, crooked or irregular.
Other symptoms may include:
- objects appear to have different sizes for each eye
- colors lose their brightness or colors do not look the same for each eye; or
- light flashes or flickering lights appear in central vision
Macular neovascular membranes (MNV) are most commonly found in people age 50 and older. The risk grows with age. This is because wet age-related macular degeneration accounts for most patients with CNVM.
People with risk factors for different eye diseases or who have an eye injury may develop MNV at a younger age.
To diagnose macular neovascular membranes (MNV), your ophthalmologist will take special photographs of your eye. They take these images using fluorescein angiography (FA) optical coherence tomography (OCT) or optical coherence tomography angiography (OCTA).
During FA, a fluorescein dye is injected into a vein in your arm. The dye travels throughout the body, including your eyes. FA captures images of your retinal blood vessels as the dye passes through them. The dye highlights abnormal areas, showing your doctor whether you have MNV.
OCT scanning creates a cross-section picture of your retina. This image helps your ophthalmologist detect abnormal blood vessels.
OCTA is like fluorescein angiography but does not use a dye. It takes pictures of the blood vessels in and under the retina.
Treatment of macular neovascular membranes (MNV) can vary depending on the underlying disease. Treatment includes anti-VEGF drugs, thermal laser treatment or photodynamic therapy (PDT). Depending on the progress of your disease, you may receive one or more of these treatments.
A common way to treat MNV is with anti-VEGF drugs. These drugs target a chemical in your body that causes abnormal blood vessels to grow within or under the retina. That chemical is vascular endothelial growth factor, or VEGF. Several anti-VEGF drugs can block the trouble-causing VEGF chemical in the eye. Blocking VEGF reduces the growth of MNV, slows their leakage, helps to slow vision loss and in some cases improves vision.
Your ophthalmologist administers the anti-VEGF drug directly to your eye in an outpatient procedure. Before the injection, your ophthalmologist will clean and numb your eye. You may receive multiple anti-VEGF injections over the course of many months. Repeat anti-VEGF treatments are often needed for continued benefit.
Photodynamic therapy (PDT)
PDT uses a light-activated drug called a photosensitizer and a special low-power, or cool, laser to target the MNV. Your ophthalmologist performs this procedure on an outpatient basis, usually in an ophthalmologist’s office. The photosensitive drug is injected into a vein in your arm. It travels throughout the body and to the abnormal blood vessels. The laser is targeted directly on the abnormal vessels, activating the drug. This causes damage specifically to those unwanted blood vessels.
After PDT, the abnormal blood vessels may reopen, so you may need multiple treatments.
Treating MNV can help stabilize your vision and prevent further vision loss. However, in many patients it is not possible to regain lost sight. In such cases, it is important to learn how to make the most of your remaining vision.
Thermal laser treatment
Another treatment for MNV is thermal laser therapy. Laser treatment is usually done as an outpatient procedure. It takes place in the doctor’s office or at the hospital.
A laser beam is a high-energy, focused beam of light. It makes a small burn when it hits the treatment area of the retina. This destroys the abnormal blood vessels, preventing further leakage, bleeding and growth.